The present invention relates to an image display unit and, more particularly, to an image display unit which is a head-mounted display (HMD) type for seeing a liquid crystal display through a magnifying lens and which includes an environmental image display device for displaying an environmental image at the peripheral portion of an observer's field of vision in order to improve the ambiance and which includes an environmental image synthesizing device for synthesizing an environmental image around an input image to increase the ambiance of the input image. The proposed image display unit is intended for use, e.g., in observing TV programs, video programs and stereoscopic images as well as for displaying an image with virtual reality, for monitoring TV games and for monitoring information fed into word processors and computers.
Recently, a head-mounted display (HMD) made on the basis of a miniaturized liquid-crystal display has been developed.
All components are mounted in a spectacle-like casing which is mounted on the head of the observer. Each of the two spectacle-like portions of the casing contain a back light, a liquid-crystal display, a diaphragm and a lens arranged in this order from the outside thereof. Therefore, when the observer puts the casing on his head, he can see an enlarged image of the liquid-crystal display.
In the above-mentioned conventional head-mounted display, only an effective area of liquid-crystal display provided with a back light is made visible and covered at its periphery by the black diaphragm. Accordingly, the observer can look at a screen appearing in the dark.
The conventional display or projector is intended to increase the reality of an image by increasing the size of its display screen and the conventional head-mounted display is intended to increase the ambiance of an image by enlarging it through a magnifying device.
The Japanese laid-open patent application No. 4-106668 describes such a conventional display unit that operates as follows:
When coordinates of a center image, as positional information, are entered by an input device, the center image generating device reads out an image corresponding to the center portion area specified by the positional information from the image stored and a peripheral image generating device takes out a peripheral image from the image storage according to the positional information. An image generating device synthesizes a final image from the center portion image prepared by the center image generating device and a peripheral image prepared by the peripheral image generating device and indicates it on an image displaying device. A thus constructed display unit provides the possibility of displaying a detailed image and a general image at the same time on a screen to clearly indicate the correlation of the two images from which one can know the position and/or connection of two referred parts on the two images.
In any conventional image display unit, wherein a display screen appears in the dark as described above, there may arise three problems that need to be solved. The first problem includes a large difference of luminosity between the center portion and the peripheral portion of the field of vision which tends to make a user's eyes tired. The second problem includes seeing the screen in the dark which may cause someone to perceive it as smaller and less powerful than it is because of not being compared with the displayed object, just as if one looked at the moon on a dark night. The third problem includes seeing an image on a screen in the dark. The observer may be puzzled with no way to judge where he is and he cannot enjoy the ambiance like seeing a movie in a movie theater or a TV program in his house.
The prior art has attempted to increase the reality of an image by physically enlarging the display screen or by physically enlarging the image itself in the case of a head-mounted display. Obtaining an image in that way does not provide the ambiance as expected by an observer despite its enlarged size. In this connection, it is necessary to consider two factors which perceptual psychology points out as follows:
The first factor is that the observer judges the screen's size by comparing it with a known (familiar to him) object that exists near the screen. The second factor is that the observer also judges the position of the screen with regard to the perspective representation and then recognizes the size of any object in the image.
By increasing only the image's size of the display without providing any clue to refer it to, make it impossible to allow the observer to feel his presence therein.
The above-mentioned Japanese laid-open patent application No. 4-106668 describes such a conventional display method that is intended to clearly display a drawing by indicating a drawing in detail at the center portion of the display screen and the same but a simplified drawing at the peripheral portion thereof. On the contrary, the present invention provides an image display system intended to increase the ambiance and the impression of a main image at a center portion of a display screen by displaying a different environmental image (e.g., an image of seats in movie theaters) around the center image. Therefore, the image display unit according to the present invention is similar to the prior art display unit only by separately processing a center portion image and peripheral portion image but it differs considerably from the prior art in its purpose and processing methods.